Skewed X-chromosome inactivation in human embryos with mosaic trisomy 16

The sex ratio and X-chromosome inactivation were analyzed in placental tissues of human spontaneous abortuses with pure and mosaic forms of chromosome 16 trisomy. The sex ratio value was found to decrease with an increase in the share of cells with the trisomic karyotype, which suggests differential survival of embryos belonging to different sexes. The pattern of X-chromosome inactivation in cells of extraembryonic mesoderm in the control group of embryos and in spontaneous abortuses with the level of trisomy 16 below 80% corresponded to random X-inactivation, whereas in most embryos with a frequency of trisomy 16 exceeding 80% skewed inactivation was observed. Our results support the hypothesis about the existence of an autosomal transfactor influencing the initiation of X-chromosome inactivation and suggest its possible localization on chromosome 16.